Quran 3:141 — The Amramites (Ali-'Imran)

GOD thus toughens those who believe and humiliates the disbelievers.

[3:140] If you suffer hardship, the enemy also suffers the same hardship. We alternate the days of victory and defeat among the people. GOD thus distinguishes the true believers, and blesses some of you with martyrdom. GOD dislikes injustice.

[3:142] Do you expect to enter Paradise without GOD distinguishing those among you who strive, and without distinguishing those who are steadfast?